A. Field of the Invention
This invention relates to a light-sensitive remote control unit for electrical appliances. More specifically it relates to a simple, inexpensive control unit actuated by the beam from a common flashlight and capable of multiple control functions of an appliance. The embodiment of the invention described herein is arranged for the control of a television set.
B. Background of the Invention
The wireless remote control of home appliances is presently applied almost exclusively to television receivers. This is probably due to two factors, namely, (a) the need to exercise frequent control of a television receiver, usually in changing channels and (b) the fact that the user is sitting or reclining at some distance from the receiver and finds it a nuisance to go to the receiver every time a control function is to be exercised.
Prior to the present invention, the commercially successful remote controls for television receivers have used sonic, or more specifically, ultrasonic transmissions as the control vehicle. In one of these systems, the user has an ultrasonic transmitting unit that is provided with a number of buttons. Actuation of a button causes a transmission at a unique frequency and an ultrasonic receiver built into the television receiver responds to that frequency by emitting an electrical control signal that brings about a corresponding control function such as channel change, etc. This system is relatively expensive and furthermore, by virtue of the manner in which it effects control within the television receiver, is not readily adaptable to receivers that were not originally constructed to accommodate it.
A less expensive wireless remote control unit that is easily fitted to existing television receivers is described in the co-pending application of Eric A. Kolm, Ser. No. 476,438 for Remote Television Control filed June 5, 1974, the disclosure of which is incorporated herein by reference. In that system the user has a simple ultrasonic transmitter that transmits on a single frequency. By simply controlling the timing of transmissions from his control unit he can cause an ultrasonic receiver at the television set to effect different control functions such as channel change and on-off switching. The present invention is directed to a control unit that is even lower in cost than this.
Another suggested arrangement uses light as the transmission vehicle. The user aims a flashlight beam at one of several photocells positioned at the television receiver, the electrical outputs of the photocells effecting the desired control functions. All such systems known to me are impractical because they can respond also to changes in the ambient light level, resulting in false triggering of the various control functions. Moreover, for multiple control functions they are characterized by either complicated and therefore relatively expensive circuitry or, on the other hand, by impractical operating procedures.